Since the time Louis Pasteur discovered the germ theory of infection, medical instruments have required sterilization to prevent contamination and the spread of infection in patients. Hospitals and other medical care providers, faced with substantial numbers of instruments to be sterilized, are in constant need of ways to increase the efficiency and speed of the sterilization process. Further, not only do the hospitals need to expedite the sterilization of the instruments, but because they cannot determine exactly when the instruments will be used, they need to provide storage facilities for the instruments after the instruments have been sterilized so the instruments remain sterile.
In order to sterilize medical instruments, hospitals typically use steam sterilizers. Steam sterilizers apply a combination of heat and humidity for a pre-determined period of time to kill all pathogenic organisms found on the instruments and the container holding them. When the containerized instruments are removed from the steam sterilizer, they are sterile. In order to keep them sterile, the prior art taught to wrap them in cotton muslin fabric or a non-woven polyolefin material. The instrument wrap attempted to keep the bacteria, dirt, dust and other contaminants off the instruments so that they would be sterile when used.
Wraps have a number of disadvantages. First, they require extra labor in wrapping the instruments. Second, wraps are susceptible to contamination and do not provide for a long shelf-life. Wraps are also disadvantageous for the reasons that they neither protect delicate instruments from damage during handling nor protect the handling health care workers from sharp items wrapped inside. Wraps also have problems in terms of what is referred to as consumables. In the case of the cotton material, the wraps need to be washed and processed further which adds extra cost. In terms of the non-woven disposable materials, the wraps must be disposed of, creating problems of excess waste.
The significant disadvantages of instrument wraps led to the use of medical instrument sterilization containers. An early container introduced in the U.S. was a metal box with a filter through the top to allow entry of steam. This container, originating from the Aesculap Corporation of Germany, had numerous disadvantages in this country. Health care workers are trained to reject any medical instrument found in a container where there was evidence of moisture or water and they are taught that steam must transfer through from the top through the bottom. In the sterilization process, the moisture-laden steam contacting the cooler medical instruments condenses and forms moisture in the bottom of the container. Then during the drying process, the moisture is removed. However, in the first available containers, complete removal of the moisture was not always easily achieved resulting frequently in the rejection of the load of instruments. Another problem with the first containers resulted when the hot container was removed from the steam sterilizer with moisture-laden air trapped inside. When the container cooled, the moisture-laden air recondensed to form moisture pools in the bottom of the container. These serious disadvantages with the first containers led to the introduction of a metal container with filters in both the top and bottom.
A number of containers have been provided with filter arrangements in the top and bottom. These containers can be generalized as generally flat on top, with two filters in the lid for a "full-size" container, and generally flat on the bottom with one or more filters in the bottom. To keep the bottom filters from coming into contact with the water and moisture that collects on the bottom of the container, the filters were isolated by either a raised dam or a gutter.
An alternative container design is disclosed in U.S. Pat. No. 4,551,311 to Lorenz and which was for a period of time embodied in a container marketed by the American Sterilizer Company (AMSCO). This container had no filter in the lid, employing a shield or umbrella-like outer cover and an inner plate for permitting the entry of sterilizing gases. The bottom of the Lorenz container was sloped to a centrally located drain opening that was controlled by thermostatically controlled valve. This container had numerous disadvantages, the primary one being the reliance on a mechanical device which was prone to failure.
The problems and disadvantages of the metal sterilization containers are significantly amplified when plastic is used as the material of construction. Plastic material cannot absorb or conduct heat as rapidly or as well as metal, which significantly affects the ability of the container to dry. Early container designs that attempted to employ the Aesculap structure in a plastic container were considered absolute failures and rejected by the medical profession.
Another type of plastic container is described in patents to Sanderson, U.S. Pat. Nos. 4,196,166, 4,416,417, 4,251,482, and 4,372,921. The Sanderson container had a single opening that served both as an inlet and outlet for the sterilizing gases as well as the condensate formed in the sterilization process. The Sanderson containers relied heavily on mechanical components which were found to be significantly disadvantageous and not widely accepted.
Another requirement of the hospitals in expediting the sterilization of medical instruments is the ability to stack two or more containers--one on top of another--in the sterilizer and have them perform the sterilization process completely and dry within the standard minimum dry time, generally twenty minutes or less. The containers with exposed filters on the top and bottom were not able to be stacked in the sterilizer for the reason that condensate flowing from an upper container would collect in the lower container which would neither dry nor complete the sterilization process adequately. The only containers that could be stacked in the sterilizer--such as the Lorenz containers because of their reliance on mechanical valves--were found to be unacceptable and hospitals were then required to alternate the positioning of their containers in the sterilizer making for a much less efficient operation. Another disadvantage of containers with exposed filters in the lid is that the aperture in the lid area is the primary area in which contaminants might enter the container.
The problems and disadvantages of the prior art have for many years created a long felt and unsatisfied need for a container that would dry in less than the standard twenty minute dry time for in-hospital sterilization. Another feature that has long been sought by the art is a container designed so that multiple containers can be stacked one on top of another in the sterilizer without the upper container draining condensate into the container stacked beneath it. It is also desirable to have a medical instrument sterilization container with no moving parts and therefore more reliable. These numerous disadvantages and problems of the prior art as well as the advantageous features described above have been provided with the medical instrument sterilization container of the present invention.